Prior to a short discussion of the related art being set forth, it may be helpful to set forth definitions of certain terms that will be used hereinafter.
The term “wireless power transfer” (WPT) (also known as power-over-the-air) refers herein to the transmission of electrical energy from a power source to an electrical, such as an electrical power grid or a consuming device, without the use of conductors. In wireless power transfer, a wireless transmitter connected to a power source conveys the field energy across an intervening space to one or more receivers, where it is converted back to an electrical current and then used. Wireless transmission is useful to power electrical devices in cases where interconnecting wires are inconvenient, hazardous, or are not possible. Wireless power techniques fall into two categories, non-radiative and radiative. In non-radiative techniques, power is typically transferred by magnetic fields using magnetic inductive coupling between coils of wire. Applications of this type include inductive powering of electric vehicles like trains or buses.
The term “power transmitter” refers herein to the infrastructure side of a WPT network. In inductory based WPT, the power transmitter includes the inductance circuitry. The term “power receiver” refers herein to the vehicle side of a WPT network.
The term “non-tracked vehicle” refers herein to on road vehicles that are not bound to moving along specific tracks, such as cars and buses, as opposed to ordinary and light trains.
Powering non-tracked vehicles over the air pose many challenges. Since a non-tracked vehicle can move lateral to the direction of advancement, there is a danger of the inductance circuits on the power transmitter side (road) and the inductance circuits on the power receiver side (vehicle) become non-overlapping and thus the WPT process becomes inefficient.
Another challenge is to deal with potential radiation hazards due to the coils positioned right under the road. Yet another challenge is to regulate the current supplied by the network to the vehicle despite a varying load. Unregulated current at the power receiver (vehicle) may lead to unlimited current and destruction of the power receiver circuits. It is also important to provide an efficient yet simple mechanism by which the power receiver (vehicle) requests energy from the power transmitter (road).